Pulp screen



Dec. 5, 1933. T. o'coNNoR 1,937,526

PULP SCREEN Filed April 12, 1932 2 sheets-sheet 1 MHH Dec. 5, 1933. T. o'coNNoR 1,937,526

PULP SCREEN Filed April 12, 1932 2 Sheets-Sheet 2 4,5 ava/6243 30 f4' 413 MQW' 417 6 pf f 2 f .fo .4a l, 6 M 27 :3|

@y Il 1 l gag 13 I dum va w/g m Patented 'Dec. 5, 1933 UNITED STATES PATENT OFFICE 14 Claims.

5 tank for movement between the walls thereof and the screen.

While the invention is adapted particularly for the treatment of wood pulp and other similar pulps utilized in the manufacture of paper, it is to be understood that it is likewise adapted for other purposes where an agitator is employed in the treatment of materials similar to wood pulp.

Screens of the general type to which my improvement relates are commonly used in the treatment of wood pulp before this pulp is utilized in a paper making machine, the primary purpose of such a screen being to disintegrate the pulpy mass and to separate fibrous matter of undesirable size and foreign materials from the pulp before it reaches the paper making machine. The screens utilized for this purpose are usually of the rotary type, and it has been found advantageous to make use of a screen in which the perforations are in the form of elongated slots extending circumferentially of the cylindrical-wall of the screen. In practice sheet bronze or other suitable material is ordinarily employed for making the screen and the Width of the slots or perforations ranges from twelve thousandths to fifteen thousandths of an inch.

While screens of this character have been found to be satisfactory from certain standpoints, such screens are objectionable due to the tendency of the particles of fibrous material in the pulp to clog the perforations in the screen and thereby prevent the pulpy material from passing through the screen in a satisfactory manner. In using a screen of this general type it is therefore customary to direct a spray of water upon the screen during its operation in an endeavor to effect the removal of the fibrous particles which collect thereon and clog the perforations. This method of maintaining the perforations free from fibrous material has not been entirely satisfactory for the reason that such pressure is exerted upon the pulp by the agitating means when it moves toward the screen that the larger fibrous particles are forced into the perforations to such an extent as to resist removal by the spray of water.

It is an object of my invention therefore vto provide in a rotary pulp screen agitating means so constructed and so arranged and operated that a minimum amount of pressure is exerted n upon the pulp by the agitating means when it moves towards and away from the screen so that the larger particles of brous material are not forced into the perforations and the screen is more'easily kept clean by the spray of water used for that purpose. Another object of my invention is the provision of an agitator so constructed that a minimum of power is required to move the same back and forth through the pulp. Still further objects and advantages of my improvement will be apparent from the description which follows.

In order that my invention may be readily understood, reference is made to the accompanying drawings in which:

Fig. 1 is a transverse sectional view of my improved screen with the agitator shown in its lowermost position;

Fig. 2 is asimilar View showing the agitator in its uppermost position;

Fig. 3 is a longitudinal sectional view of the screen shown in Figs. 1 and 2;

Fig. 4 is a transverse sectional View of a screen showing a modified form of agitator;

Fig. 5 is a longitudinal sectional view of the modified form of screen shown in Fig. 4, and

Fig. 6 is a plan view of the tank in which the rotary screen and my improved agitator are mounted.

As shown in the various figures of the drawings, my improved apparatus comprises a tank 10 substantially semi-cylindrical in shape having a curved bottom wall 11, and end walls 12 and 13. This tank may be supported at a convenient height upon a pair of end frames 14 and 15 suitably secured thereto. Pulp which has been previously treated in any desirable manner is introduced into the bottom of the trough through a pipe 16 as shown. The end walls 12 and 13 of the tank are provided with offset portions 17 and 18 having outlets 19 and 20 for the screened pulp. These offset portions are provided with bearings 21 and 22 for the opposite ends of a shaft 23 upon which the rotary screen 24 is mounted. This screen comprises the spiders 25 and 26, one of which is located in either end thereof, and these spiders may be in the form of a wheel having a hub 27 secured to the shaft 23 with spokes 28 radiating therefrom and supporting a rim 29 upon their outer ends. The rims 29 are circular in shape and have secured thereupon the screen proper comprising a curved plate 30 of bronze or other suitable material having the circumferential slots 31 therein for the passage of pulp from the lower portion of the tank into the screen, thence through the spiders in the ends thereof into the offset PQrlQllS. 17 and 1.8 of the tank for delivery means, although not shown herein.

through the outlet openings 19 and 20 heretofore referred to.

The joints between the ends of the rotary screen 24 and the ends walls 12 and 13 of the tank are closed by means of a strip 32 of canvas or other suitable flexible material having its outer edge seated in a groove 33 at the juncture of the offset portions and the end walls of the tank, this outer edge being secured to the tank by means of a strip 34 of copper or other suitable material held in place by `screws .or bolts as indicated at 35. The inner edge of the flexible strip 32 is in contact with the curved plate 30 of the screen and thus constitutes a seal to prevent the passage of any unscreened pulp from the bottom portion of the tank directly into the offset portions thereof Without passing through the screen proper.

One end of the screen shaft 23 isextended beyond its bearing 22 and has secured thereon a pulley 36 carrying a belt 37 driven by any suitable It will be understood however that the screen rotates at a speed of one to one and a half revolutions per minute when the apparatus is in use.

As disclosed in Figs. 1, 2 and 3, one form of my improved agitating means comprises a plurality of spaced bars :J8-triangular in cross-section, and as will be seen from Figs. 1 and 2 these bars are located in the bottom portion of the tank between the curved wall 11 thereof and the screen 24, and are so arranged that an angular portion 39 of each extends toward the curved wall of the tank and a side 40 thereof faces toward the screen. As will be seen from Fig. 3 of the drawings, these triangular bars extend substantially throughout the length of the tank and are carried by a pair of U-shaped hangers 41 secured to the opposite ends of the bars by screws 42. The upper ends of the hangers 41 are secured to and supported by a pair of rods 43 extending lengthwise of the tank adjacent the upper edge thereof. Surrounding-each of the rods 43 near the opposite ends thereof are clamping member 44 retained in position thereon by means of set screws 45 or otherwise. The outer ends'of the two arms of clamping members 44 are provided with alined openings to receive the upper ends of connecting rods 46 each of which has a collar 47 secured near its upper end against which a clamping member 44 is securedby a nut 48.

Elongated guide members 49 on the tank are provided with guide openings therein to receive the connecting rods 46, and coiled springs 50 are mounted on the connecting rods between the guide members 49 andthe collars 47 on the rods. This manner of mounting the agitator not only provides a resilient support therefor but enables me to utilize the coiled springs 50 for moving the agitator in a direction toward 'the screen thus minimizing the power which is required for operation of the device.

Extending transversely of the apparatus adjacent either endlthereof are cross-head members 51 carried by the lower ends of a pair of oppositively arranged connecting rods 46. Each cross-head member 51 is 'retained in adjustable position upon the connecting rods 46 by means of the lock nuts 52 as shown. Extending longitudinally of the apparatus and mounted in suitable bearings 53 in the end frames 14 and 15 is a shaft 54 one end of which is extended beyond the frame 15 and is provided with a pulley 55 carrying a belt 56 driven from any suitable source not shown. Secured near each end of the shaft 54 Within the frames 14 and 15 is an eccentric 57 provided with a flanged rim or pulley 58 operating within a guide-way formed by the crosshead 51 and an elongated bar 59 spaced therefrom and secured thereto by the threaded bolts 60.

In the operation of the apparatus the shaft 54 carrying the eccentrics 57 is ordinarily rotated at a speed of two hundred and fty to three hundred revolutions per minute, and the eccentric and connecting rod construction heretofore described operates to move the agitating means downwardly against the tension of the springs 50 on the connecting rods 46. Although this eccentric construction may be utilized if desired to move the agitating means upwardly or toward the screen, I prefer to utilize springs of such strength that the tension in the springs, when compressed by means of the eccentric construction which I have described, will be sufficient to move the agitating means in an upward direction, or in a direction toward the screen.

In the modification of my invention shown in Figs. 4 and 5 of the drawings I utilize agitator .bars which are triangular in cross-section, al-

though in this case it will be noted that the bars are arranged to extend transversely of the screen instead of lengthwisethereof as heretofore described in connection with the modification shown in Figs. 1, 2 and 3. The construction of the tank andthe means for operating the agitator shown in Figs. 4 and 5 is similar in all respects to the construction of the corresponding parts of my invention as heretofore described inA connection with Figs. 1, 2 and 3, and a detailed description of these parts is therefore not repeated.

In the form of my improvement shown in Figs. 4 and 5 the agitator bars 61 are substantially U- shaped and the upper ends. thereof are carried by the supporting rods 43. Set screws 62 or other suitable means may be utilized for adjustably mounting the upper ends of the bars 61 upon the supporting rods 43. The curved portions of these U-shaped bars are triangular in cross-section as shown in Fig. 5 while the upper ends are flattened and somewhat reduced in thickness. The bars 61 are so arranged that an angular portion 63 of each extends outwardly toward the curved bottom wall of the tank, and a side portion 64 faces thescreen 24. This arrangement will therefore be seen to be similar to the arrangement of the'triangularly shaped bars 38 utilized in the form of my invention'shown in Figs. 1, 2 and 3.

As shown in Fig. 5 of the drawings the agitator bars 61 aresubstantially in the form of an equilateral triangle, although this particular shape is not essential in the practice of my invention. I have also shown adjacent each end of the tank in Figs.,4 and 5 a triangularly shaped bar 65 arranged to fit closely against the end of the tank in orderthat efficient agitation Aof the pulp may be secured.

In the operation of my improved apparatus it will be understood that the tank in which the screen and agitator are mounted is filled with pulp substantially up to the rotary screen shaft. During the upward movement of the agitator the concaved upwardly directed faces of the triangularly shaped bars move toward the screen and operate to force the pulpy material through the perforations in the screen. In the downward movement of the agitator an angular portion of each bar is inadvance in the movement through the pulp so that there is a minimum of resistance to the movement of the agitator in a direction away from the screen. .'In both the upward .and downward movements the agitator acts to for the bars and their arrangement with respect to the screen operate to force a maximum amount of the pulp toward and through the screen, and consequently my-improved type of agitator is unusually eiiicient for this purpose.

I have also found that by the use of agitator bars of the form and construction herein described the rotary screen is effectively cleaned by the flowing action of the pulp caused by the movement ofthe agitating means therethrough. 'I'his is primarily due to the fact that the concaved faces of the bars exert a suction pull to remove the pulpy material from the screen, and the pulp is forced violently upwardly between the bars, due to their tapered formation, and this upward flow of the pulp between the bars, through the opening between the upper edges of adjacent bars into the spaces behind the bars as they move downwardly, is with sumcient force to effectively .remove from the screen the portions of fibrous material which have lodged in the per forations therein.

While I have disclosed agitator bars of certain triangular cross-sections, it is to be understood that my invention is not limited to the precise shapes and arrangements herein disclosed. It is also understood' that other forms of the means which I have' shown may be utilized for operating the agitating means. Such modifications in form, arrangement and number of -parts may be made as desired without departing from the intent of my invention as hereinafter pointed out.

Having thus described my invention, what I desire to secure by United States Letters Patent 1. In a screening apparatus the combination of a tank, a rotary screen mounted in said tank and spaced from the side walls thereof, an agitator comprising a plurality of spaced bars supported between the walls of said tank and saidv a tank, a rotary screen mounted therein and spaced from the side Walls of the tank, an agitator bar mounted for reciprocatory movement between saidl tank and said screen, said agitator bar being substantially triangular in cross-section and having an angle thereof extending toward the wall of the tank and the opposite side facing the screen, and means for causing reciprocatory movement of said agitator bar.' A

6. In a screening apparatus the combination of a tank, a rotary screen mounted therein and spaced from the side walls of the tank, an agitator comprising a plurality of parallel bars mounted for reciprocatory movement between said tank and said screen, supporting means for said bars mounted adjacent the upper edge of the tank, and means for l reciprocating said supporting means.

7. In a screening apparatus the combination of a tank, a rotary screen mounted therein and spaced from the side walls of the tank, an agitator comprising a plurality of parallel bars triangular in cross-section mounted for reciprocatory movement between said tank and said screen, supporting means for said bars mounted adjacent the upper edge of said tank, and means for reciprocating said supporting means.

8. In a screening apparatus the combination of a tank, a rotary screen mounted therein and spaced from the side walls of the tank, an agitator comprising a plurality of spaced bars triangular in cross-section mounted for reciprocatory movement between said tank and said screen, a

ing said support comprising a shaft, an eccentric thereon, a flanged rim rotatable on said eccentric, and a cross-head connected to said support and in engagement with said flanged rim.

9. In a screening apparatus the combination of a tank, a rotary screen mounted therein, an agitator mounted for reciprocatory movement between said screen and said tank, a support for said agitator, a resilient mounting carrying substantially thev entire weight of said support and said agitator and effecting movement thereof in one direction, and means for effecting movement of said support in the opposite direction.

l0. In a screening apparatus the combination of a tank, a rotary screen mounted therein, an agitator mounted for reciprocatory movement between said screen and said tank, a support for .support for said bars, and means for reciprocat- 

